Tuesday, May 29, 2007

IRIDOIDS A Review on Chemistry, Pharmacology, SAR,Extraction Methods & Structure Elucidation




Ghassemi Dehkordi, Nasrollah ;Ghannadian ,Mustafa
Faculty of Pharmacy, Isfahan University of Medical Sciences, Isfahan, I.R. Iran

The iridoids are a group of bitter tasting monoterpenoid lactones having a cyclopentano dihydropyran ring system often with glucose attachment to the hydroxyl group of the lactone ring.
Their main purpose seems to be one of the providing feeding deterrence and some are also antimicrobials , Some of these plants are used as bitter tonics e.g. Menyanthes ,Others against inflammations e.g. Euphrasia , Some have antimicrobial with a little antileukemic activity such as fulvoplumerin and allamandin and Some such as aucubin are laxative and diuretic and nonglucosid iridiods of valerianaceae are sedative.

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Tuesday, May 22, 2007

The Quassinoids, a review.





Quassinoids, (termed quassin after a man by the name of Quassi who treated fever with the bark of these plants) are bitter principles most occurring in Simaroubaceae family.

They are degraded triterpenes.

Because of the wide spectrum of their biological properties there is interest in figuring out new trends about them. One of the most important effects of them are antiviral & cytotoxic.


General structural features of the quassinoids are: 1. Most of them are C20 (tetra or pentacyclic) 2. Highly oxygenated lactones 3. Except for C4, C5, C9 & C10, there are oxygenated groups on all the other carbons.


•Main requirements for antileukaemic activity: (SAR) (as in glaucarubolone 2) are

–an a,b unsaturated ketol group at position 1 & 2 or at 2 & 3 in ring A
–an epoxymethano bridge between C8
& C11 or between C8 & C13 in ring C
–presence of a free OH group in ring A
& at C12 in addition to an ester group
at C15 &/or C6

For structural features, SAR (structure activity relationship), pharmacological effects, mechanism of action, examples of quassinoid bearing plants, biosynthesis, synthesis, extraction and ... see more






Monday, May 14, 2007

Production of Arbutin by Biotransformation of Hydroquinone Using Peganum Harmala ,Varthemia Persica and Pycnocycla Spinosa CellSuspension Cultures


Gholamreza AsgharI, Aliakbar Ihsanpourb, Azam Akbaria
a Faculty of Pharmacy and Isfahan Pharmaceutical Sciences Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
Department of Biology, Faculty of Sciences, Isfahan University, Isfahan, Iran

Abstract
Cell cultures of Varthemia persica, Peganum harmala and Pycnocycla spinosa
have been studied to evaluate their abilities to bioconvert exogenous hydroquinone.
Arbutin is an important substance that has several pharmaceutical applications;
therefore, we have established V. persica and P. spinosa cultures which seem to be
able to metabolize hydroquinone. Callus cultures of V. persica were established from
seedlings, and healthy suspensions were grown using Murashige and Skoog medium
supplemented with 2,4-D and kinetin. Exogenous hydroquinone was fed to cell
suspension cultures and biotransformation reactions were detected over 24 h of
incubation. The cultures then extracted with methanol and extracts subjected to TLC
and HPLC analysis. The V. persica and P. spinosa cultured cells in this study seem
to exhibit an ability in the glucosylation of hydroquinone to arbutin. No conversion
was observed with P. harmala cell suspension cultures. The ability of cultured plant
cells for biotransformation of substrates appears to be depended on the culture strains.
Keywords: Arbutin; Biotransformation; Cell culture; Peganum harmala; Pycnocycla
spinosa; Varthemia persica.

Sunday, May 6, 2007

A serine cluster prevents recycling of the V2 vasopressin receptor


GIULIO INNAMORATI*, HAMID M. SADEGHI*, NATHANIEL T. TRAN*, AND MARIEL BIRNBAUMER†‡
*Department of Anesthesiology and †Molecular Biology Institute, University of California School of Medicine, Los Angeles, CA 90095
Communicated by Lutz Birnbaumer, University of California School of Medicine, Los Angeles, CA, December 31, 1997 (received for review
December 22, 1997)

ABSTRACT :Receptor recycling plays a critical role in the regulation of cellular responsiveness to environmental stimuli.
Agonist-promoted phosphorylation of G protein-coupled receptors has been related to their desensitization, internalization, and sequestration. Dephosphorylation of internalized
G protein-coupled receptors by cytoplasmic phosphatases has been shown to be pH-dependent, and it has been postulated to be necessary for receptors to recycle to the cell surface. The
internalized V2 vasopressin receptor (V2R) expressed in HEK 293 cells is an exception to this hypothesis because it does not recycle to the plasma membrane for hours after removal of the
ligand. Because this receptor is phosphorylated only by G protein-coupled receptor kinases (GRKs), the relationship between recycling and GRK-mediated phosphorylation was
examined. A nonphosphorylated V2R, truncated upstream of the GRK phosphorylation sites, rapidly returned to the cell surface after removal of vasopressin. Less-drastic truncations
of V2R revealed the presence of multiple phosphorylation sites and suggested a key role for a serine cluster present at the C terminus. Replacement of any one of Ser-362, Ser-363, or
Ser-364 with Ala allowed quantitative recycling of full-length V2R without affecting the extent of internalization. Examination of the stability of phosphate groups incorporated into the
recycling S363A mutant V2Rs revealed that the recycling receptor was dephosphorylated after hormone withdrawal, whereas the wild-type V2R was not, providing molecular
evidence for the hypothesis that GRK sites must be dephosphorylated prior to receptor recycling. These experiments uncovered a role for GRK phosphorylation in intracellular
sorting and revealed a GRK-dependent anchoring domain that blocks V2R recycling.